Blaine Diversion

Fish-friendly irrigation upgrade is win-win

About the Project

The Blaine Diversion is a concrete irrigation diversion dam on the Little Lost River in central Idaho. The 45-foot-long, 8-foot-high dam provides water to about 6,376 acres of agricultural land but blocks threatened bull trout from passing between the lower and upper Lost River.

Located between the Lemhi and Lost River ranges, the 49-mile-long Little Lost River disappears at the edge of the Snake River Plain where water infiltrates into the Snake River Aquifer. The river is one of the core areas of the Upper Snake Recovery Unit for the ESA-listed fluvial bull trout. Bull trout spawn in the upper section of the river and rear and forage throughout. Without passage between the two stretches of the river, fish in the lower reach cannot return to spawning grounds in the upper Little Lost River and are stranded when flows become lethally low. Removing the concrete dam and installing a passable diversion structure will connect about 45 miles of mainstem habitat upstream of the diversion with four miles downstream.

The Blaine County Canal Company, a non-profit canal association operated by its users, owns the dam and is planning a system upgrade that will replace the diversion dam with a fish-passable sill and rock weir system with fish screening. The project also converts open ditch canals to closed pipes, conserving water and allowing more precise delivery. The result is a win-win for declining bull trout and agricultural producers in a state where advancing conservation issues can be difficult. Neighboring irrigation companies are taking notice and considering modernizing their systems.

Owner: Blaine County Canal Company
Size: 45 feet long, 7 feet wide, 8 feet high
Project Cost: $128,000
ORF Investment: Construction
Miles Opened: 4 miles
Fish: ESA-threatened bull trout
Status: Removal expected 2021

  • Open four miles of downstream habitat, reconnecting it with 45 miles of headwater reach and allowing bull trout residing in lower reach to pass to the upstream spawning grounds
  • Expand rearing and foraging habitat, eliminate entrainment, and end the risk of seasonal stranding for threatened fluvial bull trout
  • Reduce operations and maintenance costs for the project users as well as water losses through conversion to a piped system.
  • Create a model for fish passage and irrigation system improvement in the Snake River Basin.
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Project Partners

Blaine County Canal Company

Trout Unlimited

Bureau of Land Management

Natural Resources Conservation Service

U.S. Fish and Wildlife